From the related art, i.e., from German Patent No. DE 10303492, a system for monitoring the tire status is known.
The system described there discloses a method and a device for monitoring the tire status at driven wheels of a motor vehicle. Wheels are rolling devices that include elements which are able to be inflated using air, such as tires. In the standard case, the tires are made of caoutchouc or rubber and virtually impermeable to air. To monitor the air pressure, in German Patent No. DE 10303492, rotary motions of the driven wheels are recorded and the variables that are a function of the detected rotary motions are generated. In addition, the generated variables are interlinked. The monitoring then takes place as a function of the result of the logic operation. The drive torque acting on the driven wheels is also utilized in the monitoring.
In different types of tires the rolling circumference varies quite considerably as a function of the drive torque, so that a change in the rolling circumference caused by a loss in pressure is able to be compensated and is not detectable then.
German Patent No. DE 10303492 already provides a solution in this regard by taking the drive torques that are acting on the tires into account.
However, indirectly measuring tire-pressure control systems in the motor vehicle, i.e., a car or a truck, are presently not networked with other systems. Changes in the wheel circumference speed and/or changes in the natural frequency of the wheels or changes in the natural frequency spectrum of the wheel, whose measure of change is interpreted as a loss in tire pressure, are calculated with the aid of ABS wheel-speed numbers. Such a tire pressure loss is indicated to the driver when a setpoint/actual comparison of these variable quantities reaches a sufficiently large difference.